Sun girl at the so called "Long Store" where the Royal Mint has boxes of coins waiting to be transferred to a network of cash centres across the UK. Each £1 coins box is loaded with 85,000 coins and weights 750kg

Situated on the outskirts of Llantrisant to the west of Cardiff, the Royal Mint's unglamorous 35-acre site looks like any other industrial park except it is concealing the monetary version of Willy Wonka’s Chocolate Factory.

Security is airport-strict and metal detectors are used for both staff and visitors who wish to enter the site. This even extends to a complete ban on coins (including foreign currencies).

On the factory floor, eight to 10 vertical presses are working 24/7 to churn out the new 12-sided coins, which will replace old round pounds as the only legal tender on 15 October this year.

As we stepped aside from the deafening piggy bank like backdrop noise of the machines – we asked Scott Kuperus, currency security and technical expert, if the machines ever malfunction.

“As you can see we’ve got numerous presses, so we have the flexibility to bring up another press,” he said.

“Obviously, that’s because we have a tight schedule so we need to have this flexibility to maintain that output,” he added.

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By schedule, he means that the Mint has to keep up with manufacturing about 3 to 4 million coins a day so there is no place for errors.

On the day of our visit Exchequer Secretary to the Treasury, Andrew Jones MP, struck the one billionth coin and Mr Kuperus expects the Mint to strike 1.5 billion coins by the end of the year.

Hot from the press: Exchequer Secretary to the Treasury, Andrew Jones MP, paid a visit to the Royal Mint to officially mark the milestone and strike the billionth coin with the Queen’s head.

And this same tight and speedy schedule might be behind the error coins we’ve seen popping up on eBay, despite the tough quality checks.

“The quality process is embedded in every single manufacture stage. We're lucky at the Mint because even the raw materials - the metals - are manufactured here, so there are also checks at that point.”

“This means the actual chance of errors getting out from the Mint are incredible rare,” Mr Kuperus said.

“But as you can’t appreciate we are manufacturing 4 million a day so there might be a small number.”

Mr Kuperus explained that the number is so “tiny” that it is beyond what the Royal Mint can measure and that’s exactly what makes them so valuable.

According to the coin expert, it’s important to recognise the difference between an imperfection – where the design is not as clear as you would expect - and an actual error where there is a mistake.

Things you might not have known about the Royal Mint

No comment: The Mint declines to say how much bullion is kept in the vault

Tight security: There is tight airport security throughout the complex, which extends to ban on any coins being brought to the factory.

The Long Store: This room endless rows of plain cardboard boxes stacked on shelving from floor to ceiling. Each is loaded with 85,000 new £1 coin with one weighting about 750kg. The rooms also has boxes with 50p and 20p.

All change: The Royal Mint doesn't just produce coins used in the UK - it makes coins for 60 countries including Poland, Thailand and the Bahamas.

Who can go to the Royal Mint? Anyone can visit the Royal Mint Experience, which opened in May 2016. You will not be able to go to the factory floor but you'll get a glimpse of it through a window. In addition, to that you'll get guided tour and some details about how blank pieces of metal are made before being struck to become coins. You will also be given the option to strike your own coin to take home as a memento.

Hot from the press The £1 coins are surprisingly warm, moments after being minted.

The process of replacing the coins, which have been in circulation for 33 years, began in March with the release of the new 12-sided version.

“It’s been a long process of preparation of working with the industry. These six months that started at the end of March were really about making sure that the industry had time to make all their changes and in cost-effective timely way, ” Andrew Jones told the Sun Online.

Mr Jones said he anticipates the industry to be overwhelmingly ready when the old round pound coin comes out of circulation on the 15 of October.

What to do you if you've got a rare coin?

FIRSTLY, you need to make sure the coin is legit and not counterfeit.

Around one in every four old £1 coins were thought to be fake, according to the Royal Mint, so there are probably more fakers in your spare change then you realise

The Royal Mint is unable to value a coin but it can confirm whether it is real or not. They will usually supply you with a letter to confirm this.

Once you’ve found out whether the coin is real or not, you have a number of options – either selling it through a coin dealer, at auction or on eBay

Adam Lawrence, chief executive and deputy master at the Royal Mint, said many of the old round pound returned will be melted down to make new ones.

“So we’re asking everyone across the UK to make sure they check their coin jars and piggy banks for round pounds,” Mr Lawrence said.

As a general rule of thumb, the rarer the coin the more valuable it is, and we’ve also published a £1 scarcity index, based on data from Checkcheker, so you can find out the value of each of the 24 £1 coin design.